The idiot mame devs have mouse input turned off by default, you have to turn it on in your mame32 options, it is on the tab under controllers. They conviently have joysticks disabled there by default as well.
I know you don't like it, but there're good reasons why it's like this.
The biggest reason (now) is because the last time joys and mice were enabled by default (~0.85), mame.net forum was totally
flooded with questions answered with a version of "disable mice/joystick". Far beyond the normal FAQ level.
Apparently that wasn't the first time, either. Twice shot, twice shy.
Besides getting the "mouse/joy don't work" FAQ here (that would just be replaced with different FAQs anyway, see reason above), what's the problem with a default different that what you use? Just keep the same mame.ini file between versions, and you won't have to edit it.